Roger has not only the knowledge, but the very rare talent and ability to explain things in a way that we can understand.

There are lots of posts asking which lens is best, or asking if I have poor resolution, too much flare, or decentering, and more. Roger addresses the variables in lens design and manufacturing in a way that most of us can understand, and having a background as a designer, lab manager, and tester of some very tightly specified components and systems, I think he has hit it right on the head.

For those of you who like to avoid reality, let me be very clear. There is no such thing as zero tolerance. Not if you measure accurately enough. If you want the very best quality obtainable, then a nice f/2.8 zoom would be priced at $20,000 to $40,000. What a coincidence — that’s about the price range of cinema-quality zooms

Great article, thanks! It's very comforting to know that unless you have a really horrendous copy of a lens, these manufacturing defects will not really impact hard copy prints to any significant degree.

For those of you who like to avoid reality, let me be very clear. There is no such thing as zero tolerance. Not if you measure accurately enough. If you want the very best quality obtainable, then a nice f/2.8 zoom would be priced at $20,000 to $40,000. What a coincidence — that’s about the price range of cinema-quality zooms

I liked that comment too. How many times do you read someone saying something like 'for 1k or 2k I expect a perfect lens'. LOL. I could say for 10k I expect a perfect car, but reality and my expectations may not be in alignment.